1. Technical Field
The present disclosure relates to a liquid-jet recording apparatus, and more specifically to a liquid-jet recording apparatus including a multi-nozzle inkjet head to jet ink droplets for high speed printing.
2. Description of the Background Art
Inkjet printing apparatuses have been recognized as excellent products in the field of digitally-controlled electronic printing because of various advantages, such as low mechanical impact, low noise, and system simplicity. Accordingly, inkjet printing apparatuses have achieved commercial success in the fields of home-use printers, office-use printers, and so on.
Conventionally, two main types of color inkjet printing technologies have been developed: drop-on-demand type and continuous-stream type. In both types of technologies, different color inks are separately supplied through corresponding passages provided in a print head unit. The passages are provided with nozzles through which ink droplets are selectively ejected toward a recording medium. Thus, each type of printing technology needs separate ink supply systems corresponding to respective inks used for printing.
For example, for the continuous-stream-type inkjet printing, a supply source of pressurized ink is used to create a continuous stream of ink droplets. A conventional continuous-stream-type inkjet recording apparatus may employ electrostatic charging devices like that described in U.S. Pat. No. 3,373,437.
The conventional continuous-stream-type inkjet recording apparatus is disposed near a point at which a filamentous ink stream is separated into individual ink droplets, and the ink droplets are charged and guided to a proper position by a deflection electrode having a large potential difference. When printing is not performed, ink droplets are deflected into an ink capture unit (gutter) for reuse or discard. By contrast, when printing is performed, ink droplets reach the recording medium without being deflected. Alternatively, deflected ink droplets reach the recording medium while undeflected ink droplets are collected into the ink capture unit. Such a continuous-stream-type inkjet recording apparatus can operate at higher speed than a drop-on-demand type inkjet recording apparatus, and can form high quality images. However, such a continuous-stream-type inkjet recording apparatus is disadvantageous in high production cost of an electrostatic deflection mechanism employed therein and relatively frequent failures in operation.
Hence, for example, another continuous-stream-type inkjet recording apparatus is proposed like that described in U.S. Pat. No. 7,413,293. For the apparatus, by cyclically applying weak thermal pulses to a continuous stream of ink ejected from a nozzle orifice by heaters, the continuous ink stream is separated into ink droplets. In response to the applied thermal pulses, multiple ink droplets are generated at a position away from the nozzle orifice. The ink droplets are divided into deflected droplets and undeflected (straight-forward) droplets by thermal pulses asymmetrically applied from heaters disposed near an outlet of the nozzle orifice.
Then, the flying direction of the deflected droplets is changed by a gas flow and captured by a collection unit. By contrast, the undeflected droplets impinge the recording medium for printing. Alternatively, the flying direction of undeflected droplets may be changed by a gas flow and collected by the collection unit while the deflected droplets impinge the recording medium for printing. Such a configuration can obviate the electrostatic charging devices of the conventional continuous-stream-type inkjet recording apparatus to improve the control performance of droplet formation.
Further, since the electrostatic charging devices are obviated, the density at which multiples nozzles are arrayed in line can be easily set to a density corresponding to a final print density of 600 dpi to 2400 dpi.
With the proposal of such a continuous-stream-type inkjet recording apparatus as a trigger, development efforts are accelerating for achieving a page-printer-type recording apparatus in which multiple nozzles of an ink ejection head are arrayed in line at such a high density and only a recording medium is conveyed to a print area with the ink ejection head being stationary. Simultaneously, development efforts are accelerating for achieving a continuous-stream-type inkjet recording apparatus according to a new printing principle and solving technical challenges involved.